Atma Sphere

You might try making the same post at http://www.otlamp.com/ which is the website for Atma Sphere owners. I am sure someone there will give you the appropriate feedback on your question.

Happy Holidays,

Scifi

I have M60 II.2's and use only half of the output tubes since 30 Wpc is okay for me. Not much heat--no problem with the amps sitting behind the speakers a fair distance away from the listening area. Of course there would be more heat with all eight output tubes. You have to balance them and adjust bias once in a while, and need a multimeter ideally since the built-in meter is said to be poor, and that's probably beyond the capabilities, and also not to the liking, of a nonaudiophile. But hey, that isn't you, is it? After all, you posted this query on Audiogon.

The Atma-Sphere amplifiers are totally stable and absolutely reliable. The output tubes are very rugged tubes and will run for a long, long time. When replacement time does come, they are not terribly expensive and they do not have to be matched. A-S sells them at very reasonable price.

The bias on the amps remains very stable, in my experience. Over the first 30-days, you will need to monitor/adjust it every few days, but once it settles in, it will stay very stable.

All of the Atma-Sphere amps operate in Class A. Any output device run in Class A, solid-state or tube, throws off a fair amount of heat. How much heat depends on which model amp you're talking about due to the varying number of output tubes. The M-60s are modest heat producers compared to the MA-2s. The MA-2s, which I own, will definitely warm up a room.

I agree with the recommendation to visit the Atma-Sphere Owner's Group web site, www.otlamp.com The folks who post there would be happy to answer other questions you may have.